1. Field of the Invention
This invention relates to a hematologic reference control. It relates particularly to a composition which can be used as a reference standard in making hematologic determinations. Most particularly, it relates to a novel composition which may be used as a reference in calculating platelet counts in human blood and in calibrating automated and manual devices designed to measure such, such as electronic counters and bright field microscopes or the Phase Microscope.
2. State of the Art
With the advent of improved automated devices for hematological study in the past decade, there has arisen a need for stable reference controls. In response to this need, a number of stabilized controls and methods of producing such have been developed. See, for example, all of the following U.S. Patents which pertain to controls for red and white blood cell counts: U.S. Pat. Nos. 3,873,467, 3,640,896, 3,632,735 and 3,754,137. The former two patents relate to stabilized compositions of human blood cells, while the latter two relate to stabilized compositions of mixtures of blood from humans and fowl. See also U.S. Pat. No. 3,558,522, wherein is disclosed a fluid suspension containing red blood cells and synthetic latex particles which is also useful as a control for red and white blood cell counts.
Although there are a number of platelet reference controls currently on the market, they are composed of human platelets, and so suffer from a variety of drawbacks. Platelets play a key role in coagulation of human blood by disintegrating when blood escapes from the blood vessels and liberating thromboplastins which convert prothrombin to thrombin, which in turn causes clotting. Consequently, human platelets are naturally unstable outside an environment of human blood. Principal problems presented by the use of human platelets as a reference control are the tendency of the platelets to disintegrate or lyse prematurely (hemolysis), thus giving such compositions a relatively short shelf-life, and undue agglutination and agglomeration..sup.1 Because of this, a primary problem of the prior art has been in achieving stablized compositions with sufficient shelf-life to be of practical use. Even stabilized compositions of human platelets are subject to problems such as the need for preservation at or below a critical temperature by refrigeration, undesirable electrolytic effects which tend to interfere with the accuracy of electronic counters, the tendency toward undue cell association, and non-uniformity in suspension. Other common problems in the art are obtaining submicroscopic particulates with a sufficiently narrow range of mean volumes, with sufficient uniformity of shape, and with appropriate electroconductivity to be useful as reference controls. FNT .sup.1 Hereinafter the problems of agglutination and agglomeration will be collectively referred to as "cell association."